Title

data_url <- "https://datahub.io/core/global-temp/r/monthly.csv"
data_raw <- read_csv(data_url)
dataT <- data_raw %>% group_by(Date) %>% 
    summarize(Temperature=mean(Mean)) %>% 
    mutate(month=month(Date),
           year=year(Date)
           )
colors <- colorRampPalette(c("royalblue","seagreen","lightblue","lightblue","#fff987","orange","red","brown"))(500)
# colors <- colorRampPalette(c("darkblue","royalblue","seagreen","#fff987","orange","red","brown","black"))(500)
P <- ggplot(dataT, aes(x=factor(month), y=Temperature, color=Temperature, group=year))+
    geom_hline(yintercept = 0, size=15, alpha=.8, color="darkgrey")+
    geom_polygon(fill=NA)+
    scale_colour_gradientn(colors=colors)+
    scale_x_discrete(labels=month(1:12, label=TRUE))+
    coord_polar()+
    theme(axis.title.x=element_blank(),
          axis.title.y=element_blank(),
          axis.text.y=element_blank(),
          axis.ticks.y=element_blank()
         )
    # Here comes the gganimate specific bits
P+transition_reveal(year)+
    ggtitle('Year: {as.integer(frame_time)}') +
    transition_time(year)+
    shadow_trail(distance = 0.01, alpha=.2)

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## Finalizing encoding... done!